Known air ion indicators or meters employ some kind of electronic amplification circuitry in order to operate a light or meter from the minute charges obtainable from air ions. An amplifier requires additional power sources such as a power supply or a battery. Electrostatic charge meters which sometimes are used as air ion indicators employ two batteries in order to indicate positive or negative charges.
The above-mentioned requirements make portable air ion indicators or meters relatively complicated, and relatively expensive to manufacture and to operate.